三.js程序返回：“无法读取未定义的属性'0'”

Question

以下代码用于动画an object according toquaternion`数据：

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera( 75, window.innerWidth/window.innerHeight, 0.1, 1000 );

var renderer = new THREE.WebGLRenderer({antialias: true, alpha: true});
renderer.setSize( window.innerWidth, window.innerHeight );
document.body.appendChild( renderer.domElement );

var geometry = new THREE.BoxGeometry( 1, 0.3, 2 );
var material = new THREE.MeshBasicMaterial( { color: 0xf4b942 } );
var obj = new THREE.Mesh( geometry, material );
scene.add( obj );

var geometry = new THREE.BoxBufferGeometry(1, 0.3, 2 );
var edges = new THREE.EdgesGeometry(geometry);
var lines = new THREE.LineSegments(edges, new THREE.LineBasicMaterial({ color: 0x000000 }));
scene.add( lines );

camera.position.z = 5;
renderer.render(scene,camera);
var xpos_o = obj.rotation.x;
var ypos_o = obj.rotation.y;
var zpos_o = obj.rotation.z;
var xpos_lo = lines.rotation.x;
var ypos_lo = lines.rotation.y;
var zpos_lo = lines.rotation.z;

let i = 0; let m = 0;
var animate = function (quat_data) {
    requestAnimationFrame( animate );

    if (m % 5 == 0 || m == 0) {
        if (m !== 0) {i++;}

        if (i >= quat_data.length){
            obj.rotation.x = xpos_o;
            obj.rotation.y = ypos_o;
            obj.rotation.z = zpos_o;
            lines.rotation.x = xpos_lo;
            lines.rotation.y = ypos_lo;
            lines.rotation.z = zpos_lo;
            i=0; 
        }

        let quat = quat_data[i]; 

        var quaternion = new THREE.Quaternion(quat[0],quat[1],quat[2],quat[3]);
        obj.applyQuaternion(quaternion);
        lines.applyQuaternion(quaternion);

        renderer.render( scene, camera );    
    }

    m++;    
}

var animate1 = function() {

    var quat_data1 = [  [0.681492531,-0.014533572,0.711492547,-0.170668778  ], 
            [-0.81103207,0.125979118,0.555748976,-0.132257921  ],
            [-0.459080697,-0.267181198,-0.846533742,0.035103342  ],
            [0.874097952,-0.166578614,-0.244525976,0.385231457  ],
            ...

    animate(quat_data1);
}

var animate2 = function() {

    var quat_data2 = [[-0.395306087,-0.567475272,-0.168275478,-0.702416024  ], 
            [0.591221013,-0.226393713,-0.208636898,0.745435603  ],
            [-0.279990579,0.754847831,0.56444738,-0.182233852  ],
            [-0.419803039,-0.623439075,-0.538698243,-0.380648559  ],
            [0.878036311,0.088829796,-0.024437397,0.469642749  ],
            ...

    animate(quat_data2);
}

var animate3 = function() {

    var quat_data3 = [ [-0.17958507,0.232682609,-0.217296778,-0.930800793  ], 
            [-0.178598829,0.228014038,-0.2182292,-0.931927075  ],
            [-0.177601473,0.223351625,-0.219152185,-0.933029522  ],
            [-0.176574343,0.218685883,-0.220066047,-0.934113976  ],
            [-0.175533915,0.214015872,-0.22097227,-0.935177153  ],
            [-0.174483815,0.209350901,-0.221866773,-0.936217247  ],
            [-0.173407996,0.204681945,-0.222753878,-0.937238325  ],
            ...

    animate(quat_data3);
}

我省略了一些quaternion 数据并将其替换为省略号以节省空间。开始部分简单地建立了场景的几何形状。 animate 函数采用quaternions 的数组。 requestAnimationFrame 每次迭代后，m 增加 1，每次达到 5 的倍数时，执行动画代码。 （这是因为我想将requestAnimationFrame 的60 fps 转换为12 fps。）动画代码将i 增加1（移动到下一个quaternion）并应用quaternion。如果 i 超过 quaternion 数据数组的长度，则它会循环回到数据的开头并重置对象的原始方向。

还有其他三个函数animate1、animate2 和animate3，它们使用不同的quaternion 数据集来执行animate 函数。

当我单击 html 代码中的按钮以执行 animate1 时，控制台在以下行给出了问题中所述的错误：

var quaternion = new THREE.Quaternion(quat[0],quat[1],quat[2],quat[3]);

Answer 1

问题是动画 (requestAnimationFrame) 是在错误的位置执行的，并且回调目标错误。 TO回调函数只传递一个参数，即时间值。

var animate = function (quat_data) {
    requestAnimationFrame( animate );

    // [...]

    let quat = quat_data[i]; 
    var quaternion = new THREE.Quaternion(quat[0],quat[1],quat[2],quat[3]);

    // [...]
}

您所期望的是函数animate 的输入是动画数据数组，但它是单个时间值。

你必须这样做：

var animate = function (quat_data) {
    requestAnimationFrame( function() { animate(quat_data); } );

    // [...]
}